Subdomain Redirect All URLs

I added a subdomain abc.mysite.com and included redirection to a folder on the main domain (mysite.com/abc). It works perfectly.

However, it is not redirecting any URLs that are part of the subdomain. So if someone goes to abc.mysite.com/page.php I want it to redirect to mysite.com/abc/page.php. Instead it does not redirect at all.